Liquid Flow Controller And Precision Dispense Apparatus And System

ABSTRACT

Apparatus and a control system for monitoring (preferably digitally) and/or controlling pressure to a pneumatic load such as a proportional fluid control valve and using a measurement input from a fluid measurement device that responds to a flow rate, the liquid measurement input being used to control the pressure to the pneumatic load so that pneumatic load may be increased or decreased (to proportionally open or close the pneumatic valve) to change the flow rate of the fluid to a desired rate. The pneumatic load can also be adjusted (to proportionally open or close the pneumatic valve) to accommodate changes in temperature and viscosity of a fluid.

This application is a divisional of U.S. Ser. No. 12/454,611 filed May20, 2009, which is a divisional of Ser. No. 10/520,635 filed Mar. 21,2005 (now U.S. Pat. No. 7,543,596 issued Jun. 9, 2009), which is a 371of PCT/US03/22579 filed Jul. 18, 2003, which claims priority ofProvisional Application Ser. No. 60/397,053 filed Jul. 19, 2002, thedisclosures of which are incorporated herein by reference. Thisapplication is related to U.S. Pat. No. 6,348,098, ProvisionalApplication Ser. No. 60/397,162 filed Jul. 19, 2002, the disclosures ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

During the manufacture of semiconductors, many different fluids must beprecisely and accurately dispensed and deposited on the substrate beingtreated, such as deionized water, photoresist, spin on dielectrics, spinon glass, polyimides, developer and chemical mechanical polishing (CMP)slurries, to name a few. For example, in conventional apparatus for suchapplications, wafers to be processed are positioned beneath suitablenozzle that then dispenses a predetermined amount of liquid or slurry tocoat or treat the wafer. The predetermined amount is premised on pumpcycles, tubing diameters and other characteristics of the fluidcontainment environment, not only on the absolute amount or mass offluid deposited on the wafer. Typically the wafer is then rotated todisperse the deposited liquid evenly over the entire surface of thewafer. It is readily apparent that the rate dispensing and the amount ofliquid dispensed are critical in this process.

When fluid flow is stopped through the nozzle, such as between wafertreatments, the potential exists for droplets of liquid from the nozzleto form and fall onto the wafer positioned below the nozzle. This candestroy the pattern being formed on the wafer, requiring that the waferbe discarded or reprocessed. In order to avoid the formation ofdeleterious droplets on the nozzle, suckback or stop/suckback valves arecommonly used. The latter of such valves are typically a dualpneumatically controlled valve pair, with one valve stopping the flow ofliquid to the nozzle, and the other drawing the liquid back from thedispense end or outlet port of the nozzle. This not only helps preventdroplet formation and dripping at the port, but also helps preventdrying of the exposed surface of the liquid, which can lead to cloggingof the nozzle, and reduces fluid contamination at the outlet.

The coating of larger wafers (e.g., 300 mm in diameter and larger) isalso problematic, as turbulence issues arise. The rotational speed ofthe wafer is conventionally used to spread the coating fluid from thecenter of the wafer where it is applied, radially outwardly to the edgeof the wafer. However, this approach creates turbulent airflow over thewafer and can result in uneven or nonuniform coatings. Reducing the spinspeed with larger wafers reduces the turbulence at the surface of thewafer, but can introduce new problems. With the reduced speed, the fluidmoves slower across the wafer, and thus spreading the fluid to the waferedge before the fluid begins to setup or dry becomes an issue.

Pumps conventionally have been used to dispense liquids in semiconductormanufacturing operations. However, the pumps suitable for suchapplications are expensive and require frequent replacement due toexcessive wear. In addition, the footprint of such pumps may be toolarge to be justified for all but the most demanding applications.

Liquid flow controllers such as the NT 6500 (Entegris Corp., Chaska,Minn.) are available that include differential pressure measurement, butthey are not adaptable to a wide range of different flow rates and orviscosities. A modular solution to provide easily adjustable pressuredrops is desirable.

It therefore would be desirable to provide a flow measurement anddispense system that results in precise, reproducible dispensing offluid without the foregoing disadvantages. In addition, the presentinvention may be applied where precise control of fluid flow is desiredor required.

It would be further desirable to provide a motorless pump system foraccurate, repeatable dispensing of fluids.

It also would be desirable to provide a pneumatic proportional flowvalve that is linear or substantially linear, exhibits minimal pressuredrop, and exhibits minimal or no hysteresis.

SUMMARY OF THE INVENTION

The problems of the prior art have been overcome by the presentinvention, which includes apparatus and a control system for monitoring(preferably digitally) and/or controlling pressure to a pneumatic loadsuch as a proportional fluid control valve and using a measurement inputfrom a fluid measurement device that responds to a flow rate, the liquidmeasurement input being used to control the pressure to the pneumaticload so that pneumatic load may be increased or decreased (toproportionally open or close the pneumatic valve) to change the flowrate of the fluid to a desired rate. The pneumatic load can also beadjusted (to proportionally open or close the pneumatic valve) toaccommodate changes in temperature and viscosity of a fluid.

Embodiments of the present invention provides a fluid measurement devicethat produces a flow measurement signal based upon a created pressuredrop across a frictional flow element in fluid communication with theproportional fluid control valve. Fluid pressure can be measured at ornear the inlet and at or near the outlet of the frictional flow element,the measurement signals can be amplified and the resulting pressure droptherebetween can be converted to a flow rate output of the fluid beingcontrolled. The flow rate output can be sent to a controller that allowsfor one or more valves to be modulated to obtain the desired flow rate.

The present invention provides a control system adaptable to a varietyof fluids and to fluids having a wide range of viscosities. It offersaccurate and repeatable fluid flow control and dispense performance in acost-effective and flexible manner, responding quickly to real-timeprocess variations and with minimum operator involvement.

The present invention is also directed to a proportional fluid controlvalve with improved linearity and reduced hysteresis, for liquid fluidcontrollers and motorless pump systems that utilize the valve. The valveallows for smooth, gentle flow of fluid in a substantially linearfashion, with minimal turns. Preferably the valve is pneumaticallyactuated. Where temperature is not an issue, the valve can be actuatedby any suitable means, including stepper motors, linear motors, voicecoils or other force actuators.

The present invention also is directed to an auxiliary input moduleupstream of and in liquid communication with a flow measurement devicethat can be incorporated into the motorless pump system to conditionfluid prior to being presented to the flow measurement device. Thismodule allows for filling from an unpressurized source such as a barrel.The module also can compensate for inadequate or excessive liquidpressure from a pressurized feed line (house feed or a pressurizedcanister). The module also can be used to defoam the fluids used in thesystem.

The present invention provides a motorless pump system that is adaptableto a variety of liquids and feed sources such that it could allow forstandardization of numerous dispense points in a semiconductor fab andallow the customer to accommodate additional features such as filtrationand temperature control in a modular fashion.

The present invention further provides a versatile molded valve bodythat requires fewer parts compared to a machined valve. In oneembodiment, the molded valve body is designed specifically for flowcontrol and contains two sensor housings with carefully positioned flowpaths to optimize the use of space. The sensor housing or housings canbe separately formed as inserts, allowing installation in variousorientations. By installing the pneumatic and mechanical components inthe opposite ends of the valve cavity, the differential pressure of thesystem can run in reverse and the differential pressure upstream of thevalve can be recorded to monitor the supply pressure.

One embodiment of the present invention can include a set of computerreadable instructions stored on said computer readable memory andexecutable by the one or more processors, the set of computer readableinstructions comprising instructions executable to receive an upstreampressure signal, receive a downstream pressure signal, calculate anerror signal, calculate a valve control signal based on the upstreampressure signal, downstream pressure signal and error signal.

Another embodiment of the present invention, a device comprising a setof computer readable instructions stored on a computer readable memoryand executable by the one or more processors, the set of computerreadable instructions comprising instructions executable to receive anupstream pressure signal, receive a downstream pressure signal,calculate an error signal, determine a valve gain for a particular valvebased on a valve gain curve associated with that valve, wherein thevalve gain varies according to the position of the particular valve,calculate a valve control signal based on the upstream pressure signal,downstream pressure signal, error signal and valve gain.

Another embodiment of the present invention is a device comprising a setof computer readable instructions stored on a computer readable memoryand executable by the one or more processors, the set of computerreadable instructions comprising instructions executable to receive anupstream pressure signal, receive a downstream pressure signal,calculate an error signal based on proportional, integral and derivativevalues for the upstream pressure signal and downstream pressure signal,add an error gain to the error signal, determine a valve gain for aparticular valve based on a valve gain curve associated with that valve,wherein the valve gain varies according to the position of theparticular valve, calculate a valve control signal based on the upstreampressure signal, downstream pressure signal, error signal and valvegain, adaptively adjust the valve control signal based on a set of pastposition values.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an embodiment of the present invention;

FIG. 2 is a perspective view of the housing containing the pneumatic andfluid control portion of a motorless pump or dispense module inaccordance with an embodiment of the present invention;

FIG. 3 is an exploded assembly diagram of an auxiliary input module inaccordance with an embodiment of the present invention;

FIG. 4 is a schematic diagram of the differential amplifier circuitry inaccordance with an embodiment of the present invention;

FIG. 5 is a graph of valve gain in accordance with an embodiment of thepresent invention;

FIG. 6 is a flow diagram of the control system in accordance with anembodiment of the present invention;

FIG. 7 is an exploded view of a pressure transducer housing assembly inaccordance with an embodiment of the present invention;

FIG. 8A is an end view of a proportional valve in accordance with anembodiment of the present invention;

FIG. 8B is a cross-sectional view taken along line B-B of FIG. 8A;

FIG. 8C is a cross-sectional view taken along line C-C of FIG. 8A;

FIG. 8D is a cross-sectional view taken along line D-D of FIG. 8A;

FIG. 8E is an exploded view of the proportional valve of FIG. 8A inaccordance with an embodiment of the present invention;

FIG. 9A is a graph of the hysteresis of a conventional Furon valve;

FIG. 9B is a graph of the hysteresis of a conventional SMC valve;

FIG. 9C is a graph of the hysteresis of the valve of FIG. 8A-8E;

FIG. 10 is a graph of pressure drop versus flow rate for five differentviscosities;

FIG. 11 is a graph of the mass of 2-propanol flow rate over time inaccordance with Example 9;

FIG. 12 is an exploded view of an alternative embodiment of the valve inaccordance with the present invention;

FIG. 13 is a perspective view of the integral valve and sensor housingof FIG. 12;

FIG. 14A is a perspective view, in cross-section, of the fluid inletside of the valve of FIG. 12;

FIG. 14B is a perspective view, in cross-section, of the fluid outletside of the valve of FIG. 12;

FIG. 15 is a perspective view of a stacked valve unit of the valve ofFIG. 12;

FIG. 16 is a perspective view of a valve with a single sensor housing inaccordance with an embodiment of the present invention;

FIG. 17 is a perspective view of a valve with no sensor housing inaccordance with an embodiment of the present invention;

FIG. 18 is a perspective view of a single sensor housing in accordancewith an embodiment of the present invention;

FIG. 19 is a perspective view of a dual sensor housing in accordancewith an embodiment of the present invention;

FIG. 20 is a perspective view of a flow controller and on/off valveassembly in accordance with an embodiment of the present invention;

FIG. 21 is a perspective view of a sensing device in accordance with anembodiment of the present invention;

FIG. 22 is a perspective view of a flow controller and flowmeterassembly in accordance with an embodiment of the present invention;

FIG. 23A is a perspective view, in cross-section, of a valve in adownstream pressure differential configuration in accordance with anembodiment of the present invention;

FIG. 23B is a perspective view, in cross-section, of a valve in anupstream pressure differential configuration in accordance with anembodiment of the present invention;

FIGS. 24A and 24B are perspective views of a valve in accordance withanother embodiment of the present invention;

FIGS. 25A and 25B are cross-sectional views of a valve in accordancewith a still further embodiment of the present invention;

FIG. 26 is a cross-sectional view of a valve in accordance with yetanother embodiment of the present invention;

FIGS. 27A-C are several cross-sectional views of commercially availablevalves similar to the fluid control valve of the present invention, andFIG. 27D is a cross-sectional view of an embodiment of the presentinvention;

FIGS. 28A and 28B are cross-sectional views of a valve in the closed andpartially open positions in accordance with another embodiment of thepresent invention;

FIG. 29 is a timing/control diagram of the stop assist function inaccordance with an embodiment of the present invention;

FIG. 30 is a block diagram representation of a controller that cangenerate a valve drive signal according to one embodiment of the presentinvention;

FIG. 31 is a block diagram that illustrates one embodiment of thecontrol logic circuit of a controller; and

FIG. 32 is a block diagram illustrating one embodiment of a pressurecontrol circuit.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Turning first to FIG. 1, there is shown a block diagram of the liquidflow controller in accordance with a preferred embodiment of the presentinvention. A fluid control device such as a pneumatically actuated fluidcontrol valve 10 is shown having a liquid inlet line 12 and a liquidoutlet line 13 for ultimate dispensing of the liquid to a point of use,such as a substrate which can be a wafer (not shown). The liquid outletline 13 is in fluid communication with a frictional flow element 15,such that all of the liquid exiting the fluid control valve 10 entersthe frictional flow element 15. A first pressure sensor 24 such as apressure transducer, which can be integral with the fluid control valve10 housing, is positioned at or near the inlet of the frictional flowelement 15 (such as at or near the outlet of the fluid control valve 10)to sense a first pressure, and a second pressure sensor 25 such as apressure transducer is positioned at or near the outlet of thefrictional flow element 15 to sense a second pressure. Alternatively, asingle differential pressure sensing device could be used. The portionof the pressure sensor(s) that contact the fluid is preferably made ofan inert material (with respect to the fluid used in the application)such as sapphire, or is coated with a material compatible with thefluids it contacts, such as perfluoropolymer. Details of a suitablepressure sensor are illustrated in FIG. 7. Thus, sensor housing 60 has afluid inlet 61 and a fluid outlet 62 spaced from inlet 61. Pressure andtemperature sensors 64 are sealed in the housing 60 with aperfluoroelastomer O-ring 63. End cap 65 is coupled to housing 60 suchas with a plurality of stainless steel bolts or pins 66 as shown. Thesensors 64 sense pressure and temperature in the fluid path between theinlet 61 and outlet 62, and sends a signal indicative of the sensedpressure and temperature to a controller.

Referring again to FIG. 1, pneumatic proportional control valve 20, suchas a solenoid, is pneumatically connected to the fluid control valve 10.Each pressure sensor 24, 25 (or a single differential pressure sensingdevice) is in communication with a computer processor or control circuit30, such as a controller having proportional, integral and derivative(PID) feedback components. As each sensor 24, 25 samples the pressureand temperature in its respective fluid line, it sends the sampled datato the controller 30. The controller 30 compares the values andcalculates a pressure drop across the frictional flow element 15 asdiscussed in greater detail below. A signal from the controller 30 basedon that pressure drop is sent to the pneumatic proportional controlvalve 20, which modulates the fluid control valve 10 accordingly,preferably after compensating for temperature, and/or viscosity and/ordensity.

More specifically, the system preferably is calibrated for the fluidbeing dispensed using a suitable fluid such as deionized water orisopropyl alcohol as a fluid standard. For example, once the system iscalibrated to the standard, preferably experimentally, thecharacteristics of the fluid to be dispensed are inputted or determinedautomatically, such as viscosity and density, so that the fluid to bedispensed can be compared to the standard and a relationshipestablished. Based upon this relationship, the measured pressure drop(as optionally corrected for temperature, viscosity, etc.) across thefrictional flow element, is correlated to a flow rate, compared to thedesired or target flow rate, and the fluid control valve 10 is modulatedaccordingly by the pneumatic proportional control valve 20.

Independently, a suckback valve 21, that is preferably a userprogrammable proportional valve, is in communication with a proportionalcontrol valve such as a solenoid (which can be the sate or differentfrom pneumatic proportional control valve 20) and is controlled by thecontroller (or by a different controller). It is actuated when fluiddispense is stopped or in transition, thereby reducing or eliminatingthe formation of undesirable droplets that could fall onto the waferwhen the fluid dispense operation is interrupted, and drawing the fluidback from the dispense nozzle to minimize or prevent its exposure toatmosphere. The rate and extent of the suckback valve opening andclosing is controlled accordingly. Preferably the suckback valve 21 islocated downstream of the fluid control valve 10.

By controlling the pressure to the fluid control valve 10 and/orsuckback valve 21, various fluid dispensing parameters can becontrolled. For example, where the liquid to be dispensed is a lowviscosity liquid, the fluid control valve 10 can be carefully modulatedusing pressure to ensure uniform dispensing of the liquid. Similarly,the rate at which the liquid is dispensed can be controlled, as can therate at which the liquid is sucked back from the point of dispensing bythe suckback valve 21. Once the pressure-to-volume relationship of theparticular fluid control valve 10 being used is characterized, unlimitedflexibility can be obtained using the system of the present invention.Indeed, dispense pressure is a good indicator of the quality (e.g.,uniformity) of the dispense, but an “ideal” dispense pressure profiledoes not exist for all applications and is not consistent amongst allfluid control valves. The control system of the present invention allowsthe process engineer to adjust the dispense pressure to achieve the“ideal profile” for a particular process application once thecharacteristics of the fluid control valve are known.

FIGS. 8A-8E show an integral fluid control valve 10 and sensors assemblyin accordance with a preferred embodiment of the present invention. Thevalve is substantially linear, meaning that as the pressure is increasedon the actuation diaphragm, the fluid flow increases accordingly. Inaddition, the valve exhibits minimal hysteresis. Preferably the pressure(and temperature) sensors are positioned in the fluid stream and thehousing 60 is integral with the valve main housing 70, (thus sensingfluid pressure and temperature) just prior to the inlet of thefrictional flow element.

With particular reference to FIGS. 8B, 8C, 8D and 8E, valve top cap 71includes two concentric annular rings 84, 85 that define an annulargroove therebetween for receiving a synthetic rubber O-ring 72 that withpneumatic ring 74, seals the valve pneumatic diaphragm 73 in thehousing. Opposite threaded valve buttons 76 sandwich valve top diaphragm77 and valve bottom diaphragm 78, and are biased with spring 80. Theinner assembly is held together with the threaded buttons 76 that threadto stainless steel screw 75. The outer assembly is held together withvalve bottom cap 82, stainless steel pins or bolts 83, and valve top cap71. Coupled to valve top cap 71 is a push-on fitting for pneumaticconnection to the pneumatic proportional control valve 20 with suitabletubing or the like. The flow path in the fluid control valve 10 (for theinlet and outlet) is not inline to further minimize pressure drop andunswept volume as illustrated in FIGS. 27A-D. The offset flowpaths inand out of the valve allows slurry or other fluids to flow easily andwith the least amount of accumulation.

Fluid enters the valve inlet 12 and flows in linear passageway 12A untilit reaches annular cavity 90 via inlet aperture 99 therein. The fluidtends to spiral around in cavity 90, then upon the application ofpneumatic pressure to open the valve, flows into narrow annularpassageway 92 (FIGS. 8B, 8D) past diaphragms 77 and 78, and into cavity89. A spiraling fluid flow path towards the outlet (through outletaperture 85) 13 via linear path 13A is generated in cavity 89. In orderto minimize the pressure loss between cavities 89 and 90 and to optimizethe sweeping action of the fluid in the device with the pressure dropgenerated, radiused or chamfered shoulders 93 (e.g., 0.04″) can beintroduced to the sealing surfaces of the valve. Preferably the fluidinlet path 12A and the fluid outlet path 13A are located along thetangential (rather than through the center axis) of cavities 89 and 90,respectively, to assist the fluid in flowing uniformly and to minimizepressure drop and accumulation.

By controlling the pressure entering the push-on straight fitting 86,the amount that the valve pneumatic diaphragm 73 deflects is controlled.The more pressure in pneumatic cavity 88, the more the pneumaticdiaphragm 73 will deflect, pushing on the top valve button 76, whichcauses diaphragms 77 and 78 to deflect, the spring 80 to compress, andunseats diaphragm 78 from the valve seat or shoulder 93 that partiallydefine passageway 92 (FIG. 8D), causing the valve to open. Morespecifically, the valve is designed so that the spring 80 and pneumaticpressure counter each other. The spring 80 pushes on all threediaphragms, causing the bottom diaphragm 78 to seal the main valve bodyby seating against shoulder 93. When pneumatic pressure is introduced,it opposes the spring 80. Once enough pressure is applied, the spring isno longer able to hold the valve closed. The spring compresses, causingthe diaphragms to deflect in the direction of the compressed spring,opening the valve. The greater the pneumatic pressure, the more thespring 80 compresses, and the more the valve opens.

Besides the suckback option, the speed that the fluid control valvecloses also can effectively control the liquid height at the dispenseend or outlet port of the nozzle, and in many cases will be able toreplace a suckback valve option altogether. This is possible because ofthe two fluid diaphragms of the valve design. When the valve closes, thepressure is relieved in the pneumatic cavity and the spring load takesover and forces the valve bottom fluid diaphragm 78 (FIG. 8D) to engageat the valve seat seating location. As the fluid diaphragm 78 engages,fluid diaphragm 77 bows outwardly towards the pneumatic cavity. Thisdisplacement can cause a small suckback effect.

The controller can include an idle feature that significantly reducesthe differences in response time from valve to valve. Depending upon theopening pressure requirements for a given valve, the idle pressure canbe adjusted to yield an equal response time from unit to unit. The idlepressure is the pressure provided to the pneumatic cavity when the valveis not being actuated to produce a flow. Thus, if a particular valverequires 40-psi pneumatic pressure to open, and another requires 30-psipneumatic pressure, the idle pressure can be set for 15-psi and 5-psi,respectively. As a result, both valves require a 25-psi change ofpneumatic pressure to open, in approximately the same amount of time.The valve idle feature also acts as a nitrogen purge for the system at aminimal setting requirement. The valve can be held open to allow aminimum level of purge gas, preferably nitrogen, to bleed from thepneumatic proportional control valve to provide a safety purge insidethe system enclosure, particularly where the electronics are located.

FIG. 30 is a block diagram that illustrates one embodiment of acontroller 2700 that can generate a valve drive signal to throttle/openpneumatic proportional control valve 20. Controller 2700 can include apower supply 2702, a house keeping processor 2704, a pressure circuit2705, an auxiliary function circuit 2706, a control valve driver 2708, asuckback valve driver 2709, a comport interface 2710, an I/O circuit2711 and a control processor 2712. Control processor 2712 can includeflash memory 2714 that can store a set of computer readable instructions2716 that are executable to generate a valve control signal based onpressure signals received from the pressure circuit as described inconjunction with FIG. 6. Various components of controller 2700 cancommunicate through data bus 2718. It should be noted that whilecomputer readable instructions 2716 are shown as software at a singleprocessor, computer readable instructions can be implemented assoftware, firmware, hardware instructions or in any suitable programmingmanner known in the art. Additionally, the instructions can bedistributed among multiple memories and can executable by multipleprocessors.

In operation, power supply 2702 can provide power to the variouscomponents of controller 2700. Pressure circuit 2705 can read pressuresfrom upstream and downstream pressure sensors and provide an upstreamand downstream pressure signal to control processor 2712. Controllerprocessor 2712 can calculate a valve control signal based on thepressure signals received from pressure circuit 2705 and control valvedriver 2708, in turn, can generate a valve drive signal based on thevalve control signal. The generation of the valve control signal canoccur according to the methodology discussed in conjunction with FIG. 6,below. This methodology can be implemented as software, or othercomputer readable instructions, stored on a computer readable memory(e.g., RAM, ROM, FLASH, magnetic storage or other computer readablememory known in the art) accessible by control processor 2712.

With respect to other components of controller 2700, house keepingprocessor 2704 can be a general purpose processor that performs avariety of functions including directing communications with otherdevices or any other programmable function, known in the art. Oneexample of general purpose processor is a Intel 8051 processor.Auxiliary function circuit 2706 can interface with other devices.Suckback valve driver 2709 can control a suckback valve (e.g., suckbackvalve 21 of FIG. 1). Comport interface 2710 and I/O circuit 2711 canprovide Various means by which to communicate data to/from controller2700. Additional components can include a supervisor unit 2720 that canperform device monitoring functions known in the art, various eeproms orother memories, expansions ports or other computer components known inthe art.

FIG. 31 is a block diagram that illustrates one embodiment of thecontrol logic circuit of controller 2700 that can generate a valvedrive, signal to throttle/open proportional control valve 20. Several ofthe components of controller 2700 are illustrated including controlprocessor 2712, comport interface 2710 and supervisor unit 2720.Additionally, an expansion port 2802 is shown. Expansion port 2802 canbe used to add daughter boards to expand the functionality of controller2700.

In the embodiment of FIG. 31, the functionality of house keepingprocessor 2704 is split into three portions: processing portion 2806,memory device portion 2808 and dual port RAM portion 2810. Memory deviceportion 2808 can include various memories including Flash Memory, RAM,EE and other computer readable memories known in the art. One advantageof providing Flash Memory to house keeping processor 2704 is that itallows easy downloads of firmware updates via, for example, comportinterface 2710. Additionally memory device portion 2808 can includefunctionality for chip selections and address decoding. It should benoted that each of memory device portion 2808, dual port RAM portion2810 and processing portion 2806 can be embodied in a single processor.

Control processor 2712 can include flash memory 2714 that can store aset of computer executable instructions 2716 that are executable togenerate a valve control signal based on pressure signals received fromthe pressure circuit as described in conjunction with FIG. 6. Controlprocessor 2712 and processing portion 2808 of the house keepingprocessor can share data, in one embodiment Of the present invention,through mutual access to dual port RAM portion 2810. Control processor2712 and processing portion 2808 of the house keeping processor can bedriven by a single system clock 2812 (e.g., a 20 MHz clock) or differentsystem clocks.

FIG. 32 illustrates one embodiment of the pressure control circuit 2705.Pressure control circuit 2705 can include upstream pressure inputs 2902and downstream pressure inputs 2904 that come from the upstream anddownstream pressure sensors, respectively. The input upstream anddownstream signals can be amplified and filter prior to being convertedto digital signals by A/D converters 2905 and 2906. As shown in FIG. 32,pressure control circuit 2705 can also generate a differential pressuresignal, which can be converted to a digital signal by A/D converter2908. The pressure control circuit can be calibrated by calibrationcircuit 2910 that can include hardware and/or software to compensate forchanges in sensor readings based on a known pressure applied to thepressure sensors.

Additionally, pressure control circuit 2705 can use receive upstream anddownstream input temperature signals (e.g., at inputs 2920 and 2922),which can be amplified and changed to a digital signal at A/D converter.One or both of the pressure sensors 24, 25 (or the differential pressuresensor) each can include a temperature sensing device for sensing thetemperature of the fluid at their respective positions (e.g., at or nearthe frictional flow element inlet or outlet, as the case may be) whichcan provide the input temperature signals to inputs 2920 and 2922.Alternatively, temperature sensors can be separate from the pressuresensors. The sensed temperatures are communicated to the controller,where a proper fluid flow correction is calculated and a signal sent tothe pneumatic proportional valve 20 based upon the calculation tocorrect for temperature variations. This operation is preferred sincethe pressure sensor itself can generate heat that is absorbed by thefluid and can effect the fluid flow characteristics in the system; localtemperature changes at the sensor face can alter the output of thesensor. Other embodiments of the present invention can correct fortemperature error based on, for example, the voltage drop across aconstant current device, such as the pressure sensors themselves.

FIG. 4 illustrates another embodiment of a pressure control circuit2705. As shown schematically in FIG. 4, the pressure sensors 24, 25preferably use two instrumentation amplifiers: one for upstream pressureand the other for the downstream pressure. Digital gain and offsetcontrols are used to calibrate each sensor automatically or manually.These two analog pressure signals can be converted with an analog todigital converter and the differential pressure derived in software bysimply subtracting the values. One drawback with this technique is thecompromise of resolution and common mode. The analog to digitalconverter has to convert each signal and mathematically remove thecommon mode. Increased resolution of the analog to digital converter ispreferred to obtain the required differential pressure. For example, ifthe downstream pressure is 15 psi and the differential pressure for thisflow rate is 0.1 psi, the upstream pressure would be 15.1 psi. If fullscale pressure is 30 psi, which converts to 5.00 Vdc (15 psi=2.50 Vdc),each converter has to be configured to measure up to the peak pressure(30 psi). Since 15.1 psi is 2.517 Vdc, the differential pressure signalis 0.017 Vdc (out of 5.00 Vdc). By adding a third amplifier inelectrical communication with each analog to digital converter, thecommon mode is removed and the analog to digital converter only has toresolve the maximum differential pressure, which is much less than thecommon mode. Thus, the full scale differential pressure in the aboveexample is equal to 5 psi which converts to 5.00 Vdc. This increases theresolution by a factor of 6.

The gain of the differential pressure amplifier also can be increasedwhich further increases the resolution of the differential pressuresignal. This also can be done with a single differential pressure sensorbut the independent signals upstream and downstream pressures, in oneembodiment, are not ascertained.

An analog to digital converter for the upstream and downstream pressurealso preferably is included. These separate pressures can then be usedfor monitoring the upstream and downstream pressures and to determineprocess changes (e.g., filter change-out). They also can be usedseparately for single pressure control, which can be used in theviscosity calculations.

FIG. 6 is a flow chart illustrating one embodiment of a controlalgorithm for modulation of the flow control valve 10. The algorithm canbe implemented by a controller (e.g., controller 30 of FIG. 1) executinga set of computer instructions stored on a computer readable memory(e.g., RAM, ROM, magnetic storage device or any other computer readablememory known in the art) and can include techniques taken from a Fuzzylogic and elements from an adaptive controller. Thus, the controller isa linear control system that is based on a dynamic model. Adaptation orintelligent control can be used for greater accuracy, where desired. Theadaptation control can use a nonlinear optimizer to improve the overalloperation of the control system and is within the skill in the art. Oneembodiment of a controller is illustrated in FIG. 30.

More specifically, with reference to FIG. 6, the controller, at step902, can read upstream and downstream pressure signals from, forexample, analog to digital controllers associated with the upstream anddownstream pressure sensors (e.g., A/D converters 2905 and 2906). Atthis point, the upstream and downstream pressure signals can be voltagesamplings (i.e., digital samplings) representing the analog voltagesproduced by the pressure sensors. At step 904, the controller can alsoread a temperature based on a temperature sensor reading or calculate atemperature based on the current flow through a sensor and correct theupstream and downstream pressure signals for temperature using anytemperature correction algorithm known in the art. At step 906, thecontroller can filter the upstream and downstream pressure signals and,at step 908, convert the pressure signals to pressure values, which canbe stored in memory (step 909).

The controller, at steps 910 and 911, can calculate the integral andderivative values and any corrections thereof, for the upstream anddownstream pressures. Calculation of integral and derivative values canbe performed according to any method known in the art. The controllercan also calculate (step 912) and store (step 914) the difference inupstream and downstream pressures. At step 916, the controller cancalculate an error signal based on the derivative and integral valuesfor the upstream and downstream pressures and, at step 918, store thevalues for the error signal. In one embodiment of the present invention,an error gain can be added to the error signal at step 920. This canhelp compensate for low signal values at low pressures.

At step 922, the controller can read a valve gain. One embodiment of avalve gain curve is shown in FIG. 5. This curve adjusts the gain of thesignal that will be applied to the valve proportionally to the currentposition. The gain curve implemented in software allows the system tocorrect for variations from valve to valve. In addition to correctingfor variations in a particular valve, the valve gain curve can alsocompensate for overshoot, undershoot, and response time. In FIG. 5,valve gain curves for two valves, valve A (line 500) and valve B (line501), are shown. The curves for each valve (or class of valves) can bedetermined empirically and be stored in the controller's memory. Thecurve can be used to adjust the gain of the valve control signal basedon the current valve position.

In the graph of FIG. 5 the x-axis represents a valve position and they-axis represents the gain. In one embodiment of the present invention,each curve is created using four (4) points: maximum gain; minimum gain;slope starting point and slope ending point. The maximum gain typicallystarts at the off position of the valve and extends to the slope staringposition. The minimum gain starts at the slope ending position and endsat 100% point of the valve stroke. The actual slope is a linear decreasein gain from the slope starting point to the slope ending point. Thecontroller can read the valve gain curve for the respective valve andadjust the valve control signal accordingly. For example, when the valveA is between lines 502 and 504, the controller can read the valve curve,at step 922, and adjust values for the control signal to account for thehigh gain. The curve allows for the gain of the valve signal to remainhigh when valve A is positioned between lines 502 and 504 to overcomethe forces that are holding the valve closed. At the point where thevalve is actually opening, the controller can adjust the control signalto account for the decreasing gain based on the valve gain curve andvalve position. The controller can adjust the control valve signal toaccount for the valve gain at any point along the valve gain curve. Itshould be noted, that the valve gain curves illustrated in FIG. 5 areprovided by way of example only, and the controller can adjust the valvecontrol signal based on any valve gain curve stored in any computerreadable memory accessible by the controller.

At step 924 a control signal can be generated based on the error signaland pressure values and written to a digital to analog converter (e.g.,a control valve driver). The digital to analog converter can produce ananalog valve drive signal to drive a valve. Embodiments of the presentinvention can also include a valve integration step (e.g., step 926) toslow the valve control signal and an adaptive adjustment step (e.g.,step 928). The adaptive adjustment step can read a predefined number ofstored previous position values that can be used to adjust a currentvalve control signal.

In addition, the controller can also perform monitoring step 930, whichcan be part of the adaptive adjustment. This function compiles data inreal time such as point overshoot, undershoot, settling time, loopstability and percent error. During the setup mode the data compiled isanalyzed by the controller and which adjusts control values to optimizethe performance (i.e., performs adaptive adjustment step 928).

It should be noted that the controller can also adjust the valve controlsignal to compensate for viscosity changes. Since the viscosity of thefluid changes the delta P measurements for similar rates, correctionsmust be made. One method of correction is comparing current delta P andrate to a delta P and rate of a standard such as isopropyl alcohol orwater. The differences can then be entered by the user. Another methodis to measure internal parameters and compare them to predeterminedsimilar parameters and internally compensate for the differences. Thethird method uses factory created curves for different fluids; multiplecurves can be Stored in the controller and selected by the user.

Various control parameters can be set to ensure proper operation of thesuckback valve over a wide variety of applications. For example,suckback valve “off time” adjusts the time of the ON to OFF pressuretransition. This is the time to move the valve diaphragm from it's fullyextended position to the suckback position. Moving this too fast cancause the column of fluid to pull a bubble of air into the column orcavitate. Suckback valve “on time” adjusts the time of the OFF to ONpressure transition. This is the time necessary to move the end of thevalve diaphragm from the suckback position to the fully extendedposition. Moving this too fast can cause the fluid column to “bulge”,which can deleteriously change the actual dispense rate. There are twoother settings: Suckback On and Off pressure settings. These twoadjustments determine the distance that the valve will move creating theamount of suckback desired. The greater the difference in this pressurewill increase the amount of suckback. Both On pressure and Off pressureare used for two reasons: to accommodate the differences in differentvalves of similar type; and to adjust for non-linearity in differentvalves and other system configurations. This entire action can also bedelayed to separate the stop action of the control valve and suckbackaction. In some applications the suckback valve can be used to assistthe control valve in the stopping action of the fluid with a separatesuckback position actuated during the fluid stop action, as shown inFIG. 29. This assist function can also be programmed as a percentage ofthe stop action loaded as part of the beginning of stop or the ending ofstop. The normal suckback position would then be used for suck backfollowing a delay if programmed. Turning now to FIG. 2, housing 100 isshown containing the various components of the present invention.Preferably the electrical components, such as the LED board 105 and mainprinted circuit board 106, and the pneumatic proportional valve manifold110, are isolated from the fluids, such as the frictional flow element15 and the fluid control valve 10. Fluid enters the main fluid controlvalve 10 in a fluid inlet (not shown). The fluid is then, directedthrough the valve and into the frictional flow element 15, which in theembodiment shown, includes a relatively short straight portion 15B thatis then wound helically and terminates in another relatively longerstraight portion 15A where the second pressure (and temperature) sensingoccurs. The frictional flow element 15 can be a tube or conduit or abundle of parallel hollow fiber tubes, for example, of sufficient,dimensions to create a measurable pressure drop as the fluid flowstherethrough. Other suitable frictional flow elements include aserpentine channel such as in a block of polymeric material, porousmembranes, frits and filters. Preferably the frictional flow elementavoids 90° turns that could promote clogging or excess turbulence whichcan cause shearing. Although the frictional flow element 15 can bestraight, most preferably the frictional flow element 15 is a helicalcoil to save space, the diameter and length of which depend in part onthe flow rate. Thus, the diameter and length of the frictional flowelement 15 is a function of the pressure drop needed so that “noise”becomes negligible. For a given fluid, length of tube, and systemconditions, the smaller the diameter of the tube, the larger thepressure drop. The pressure drop will increase as the viscosity of thefluid increases for a given tube geometry. For example, in the case ofdispensing Deionized Water for a fluid control valve 10 sized for africtional flow element 15 of ¼ inch OD tubing and wall thickness ofabout 0.047″ at a length of about 40″, a maximum flow rate ofapproximately 2 liters per minute can be produced depending also onsystem conditions, e.g., supply fluid pressure, supply pneumaticpressure, and system pressure drops external to the device. Flow rangescan be optimized for a given dispense/flow condition by simply changingthe geometry of the frictional flow element 15. Preferably the internaldiameter of the frictional flow element is the same or substantially thesame as the internal diameter of tubing or other flow paths downstreamof the element 15 in order to minimize or eliminate transition of fluidflowing out of the element 15. The flow through the frictional flowelement 15 can be either laminar or turbulent flow. The fluid path isthus as follows: fluid enters the fluid inlet of the fluid control valve10, flows through the valve (and past pressure and temperature sensors)and into the inlet of the frictional flow element 15, through thefrictional flow element 15 and out the frictional flow element outlet(and past pressure and temperature sensors positioned upstream anddownstream of the frictional flow element 15 outlet). The flexibility ofthe present design allows for easy interchangeability of the frictionalflow element 15 in an embodiment of the present invention, based uponflow and/or fluid characteristics, for example.

Other types of devices Used to generate pressure drop can result inunwanted side effects or are more suited to industrial processingapplications. These negative effects include uncontrolled and excessiveentrance and exit pressure losses, local regions of reverse flow or eddycurrents, and trap zones. These alternate pressure drop elements includethe Venturi tube, the flow nozzle, the orifice family (thin-plate squareedged, quadrant edged, eccentric & segmental), centrifugal, and linearresistance.

The examples below demonstrate a set of frictional flow element,specifications:

A helical coil having an inside diameter 0.0625″ which is 20 inches longand has 2.5 turns would typically flow water at room temperature between0.5 cc/sec and 5 cc/sec.

A helical coil having an inside diameter 0.156″ which is 40 inches longand has 5.5 turns would typically flow water at room temperature between1 cc/sec and 30 cc/sec.

A helical coil having an inside diameter 0.250″ which is 20 inches longand has 2.5 turns would typically flow water at room temperature between0.5 lpm and 5 lpm.

A helical coil having an inside diameter 0.375″ which is 20 inches longand has 2.5 turns would typically flow water at room temperature between2 lpm and 10 lpm.

In certain applications the pressure of the fluid entering the fluidinlet 12 (FIGS. 1 and 8C) may be too low or too high. In order toregulate the fluid pressure, an auxiliary input module 200 as shown inFIG. 3 can be used upstream of the dispense module. The auxiliary inputmodule 200 has a main body or reservoir 90 and four normally closed (dueto the bias of springs 97) poppet valves 91 secured between module base92 and cover 93. Four fluid fittings 94 and 94A are threaded to base 92as shown. One fitting is a pressure port, another a vacuum port, another(94A) a fluid input and another a vent. Four push-on fittings 95 aresecured to cover 93 and provide nitrogen to actuate poppet valves 91,which in turn will open flow to ports 94 and 94A. A fluid outlet 98 isprovided at the bottom of main body 90 as shown. Level sensors 96 aresecured to main body 90 with bracket 101 and sense the fluid level inthe module main body or reservoir 90. A filter (not shown) can beprovided in the main body 90.

To fill the module 200 with a pressurized fluid source, the inlet andvent valves can be opened substantially simultaneously, and pressurizedfluid flows into the module 200 for a certain duration or until acertain fluid level is achieved, as sensed by the level sensor(s) 96.The vent valve can be used to equalize the pressure as the inlet valveallows fluid to enter the reservoir 90. The inlet and vent valves arethen closed, the fluid supply pressure valve is opened, and the fluidcontrol valve 10 is opened when fluid flow to the system is desired.

If the fluid pressure from the source is too low for proper operation,pressure can be applied following the fill cycle to boost the supplypressure. This can be applied continuously or only when required.Similarly, pressure can be applied where necessary when fluctuations influid supply pressure occur.

If a non-pressurized source is used, inlet and vacuum valves can beopened substantially simultaneously. The vacuum valve is used to drawfluid in from the fluid source.

The module 200 also can be used as a defoamer. Specifically, the fillportion of the cycle is as described above for a pressurized fluidsource. Once the reservoir 90 is filled to the desired level, the inletand vent are closed and vacuum is applied to the fluid for auser-programmable time or desired time, thereby removing bubblestherefrom.

In an alternative embodiment, where, for example, space reduction is ahigh priority, the valve shown in FIGS. 12-23 can be used. Like thevalve of FIG. 8, the valve top cap 71′ of FIG. 12 includes twoconcentric annular rings 84′, 85′ that define an annular groovetherebetween for receiving a synthetic rubber O-ring 72′ that with toppneumatic ring 74′, seals the valve pneumatic diaphragm 73′ in thehousing. Opposite threaded valve buttons 76′ sandwich valve topdiaphragm 77′ and valve bottom diaphragm 78′, and are biased with spring80′. The inner assembly is held together with the threaded buttons thatthread to stainless steel screw, bolt or pin 75′. The outer assembly isheld intact with valve bottom cap 82′, stainless steel pins or bolts83′, and valve top cap 71′. Coupled to valve top cap 71′ is a push-onfitting for pneumatic connection to the pneumatic proportional controlvalve 20 with suitable tubing or the like. The flow path in the fluidcontrol valve 10 (for the inlet and outlet) is not inline to furtherminimize pressure drop and unswept volume as described in FIG. 27D. Theoffset flowpaths in and out of the valve allows slurry or other fluidsto flow easily and with the least amount of accumulation.

The valve housing 70′ is preferably a molded design, with the sensorhousing(s) integral with the valve. Unlike the sensor housing 60 of FIG.8, the integral embodiment requires only a single sensor end cap 65′,significantly reducing the number of parts involved, and eliminatingmachining burrs that can cause catastrophic failures.

In the embodiment of the valve housing shown in FIGS. 12-14, fluidenters the inlet of the valve inlet 12′ and flows in linear passageway12A′ until it reaches annular cavity 90′ via inlet aperture 99′ therein.The fluid tends to spiral around in cavity 90′, once the valve isopened, and then flows into a narrow annular passageway past the twofluid diaphragms and into a second cavity as was the case with theprevious embodiment as shown in FIGS. 8B and 8D. A spiraling fluid flowpath towards the outlet 13′ through an outlet aperture (not shown) vialinear path 13A′ is generated in the second cavity 89′. In order toimprove the pressure loss between cavities 90′ and 89′ to optimize thesweeping action of the fluid in the device with the pressure dropgenerated, radiuses or chamfers (e.g., 0.04 inches) can be introduced tothe sealing surfaces of the valve as before. Preferably the fluid inletpath 12A′ and the fluid outlet path 13A′ are located along thetangential (rather through the center axis) of cavity 89′ and 90′,respectively, to assist the fluid in flowing uniformly and to improvepressure drop. Inlet 12′ and outlet 13′ can have external threads asshown, for convenient coupling to suitable hosing, for example.

Positioned in flow path 13A′ downstream of the first and second cavities90′ and 89′ is a first sensor housing 60′. The sensor housing 60′ is influid communication with the second cavity 89′ and with outlet 13′.Pressure and/or temperature sensors 64′ are sealed in the housing 60′such as with a perfluoroelastomer (KALREZ) O-ring 63′. End cap 65′ iscoupled to housing 60′ such as with a plurality of bolts or pins 66′ asshown. The sensor(s) 64′ sense pressure and/or temperature in the fluidpath between the inlet and outlet of the sensor housing 60′, and send asignal indicative of the sensed values to a controller.

This embodiment of the valve also includes a second sensor housing 160′,which is preferably identical in construction to sensor housing 60′. Thesecond sensor housing 60′ is in fluid communication with inlet 112′ andoutlet 113′ spaced from inlet 112′ as shown in FIG. 13.

Accordingly, the valve of this embodiment functions as follows, withparticular reference to FIGS. 14A and 14B. The fluid inlet flow to thevalve enters inlet 12′ and flows through passageway 12A′ to the firstvalve cavity 90′ where the fluid is contained until the valve is opened.Once the valve is opened, the fluid flows from the first valve cavity90′ through an aperture to the second valve cavity 89′. From the secondvalve cavity 89′, the fluid exits via an outlet aperture and enters thefirst sensor housing 60′ where the pressure and/or temperature of thefluid is sensed and recorded and/or transmitted to the controller. Thefluid exits the valve assembly through outlet 13′ and passes through africtional flow element, preferably a coiled tube (not shown), and thenre-enters the valve assembly via inlet 112′ as shown in FIG. 14B. Thefluid flows to second sensor housing 160′, where the pressure and/ortemperature is again sensed and recorded and/or transmitted to thecontroller. After exiting the second sensor housing 160′, the fluidpasses through the valve assembly through a carefully positioned flowpath to optimize the usage of space, and returns to the same face of thedevice where it originally entered.

By designing the valve assembly to have the pneumatic features on oneside and the valve mechanical features on the other side, multiple valveassemblies can be stacked into a single unit, further reducing spaceoccupancy as well as cost. Thus, as shown in FIG. 13, sensor housings60′ and 160′ are equally sized and configured, and the sensor housing60′ is spaced from outlet 113′ the same distance. that the sensorhousing 160′ is spaced from inlet 112′. Accordingly, if two such valvebodies are vertically stacked, the valve cavities will be verticallyaligned, and the sensor housings will be vertically aligned. One exampleof such a stackable valve assembly is illustrated in FIG. 15, where themiddle cover 171′ is designed to have internal detail of both the topcap 71′ and the bottom cap 82′ in order to accept the pneumatic sidecomponents and the mechanical side components of the valve. Thestackable valve embodiment is particularly useful for multiple points ofdispense where space constraints exist. Additional advantages includeelimination of part duplication, as only a single proportional manifoldis required, only a single LED and main PC board is required, only asingle casing and cable set is required, and only a single set ofnitrogen supply lines and fittings is required. Applications includechemical mixing (ratio-metric control), synchronized dispense ofseparate fluids, independent dispense to two separate points ofdispense, integrated independent or dependent control, and continuousuninterrupted dispense.

The convenient design of the valve assembly enables substantialversatility. For example, FIG. 16 shows an assembly having a valve and asingle sensor housing. The sizing of the various components of the valveis preferably consistent with the valve of FIG. 13, to maintainstackability if desired, and to allow for an additional sensor housing,such as that shown in FIG. 18, to be added if desired. Indeed, byproviding removable sensor housing inserts of FIG. 18 as separatecomponents, devices with one or more sensor housings can be constructedwherein the sensor housings are placed upside-down (relative to thevalve cavity) to assist in facilitating bubble removal.

The various components can be formed as molded inserts. For example,FIG. 17 shows a valve having no sensor housings. FIG. 19 illustrates adouble sensor housing insert. The inlets 112′, 212′ and outlets 13′,113′ of the sensor housing are formed with external threads for easyattachment to the valve. The inserts for the sensor housing portions ofthe valve assembly enable many different assembly configurations, andare able to be replaced with inserts to mold the sensor housingsupside-down to help facilitate bubble removal depending upon theorientation of the valve when it is installed, as discussed above.Similarly, the interchangeability of the pneumatic and mechanicalcomponents allows the inlet and outlet of the molded valve to bereversed for upstream or downstream pressure control. By installing thepneumatic and mechanical components in the opposite ends of the valvecavity, the differential pressure of the system can run in reverse andthe differential pressures upstream of the valve can be recorded insteadof the pressures downstream. This allows the user to monitor the supplypressure to the system unit instead of the pressure downstream closer tothe dispense point. The downstream configuration and upstreamconfiguration are illustrated in FIGS. 23A and 23B, respectively. Thesefigures illustrate the versatility of the molded valve design in thatthe pneumatic components and the mechanical components can be installedinto either side of the valve depending on whether a pressure dropupstream or downstream of the valve is desired. The location of thesensors also provides a monitor of the customer's system conditions, notjust the conditions of the instant device.

FIGS. 24A and 24B illustrate a molded component configured for a flowcontroller with the ability to mate with a Mykrolis LHVD style filterthrough the three ports located on the bottom of the device (vent, inletand outlet ports). This design is capable of accepting an LHVD stylefiltering device.

A conventional bubble sensor can be used in the present invention. Abubble sensor sends a modulated signal to a controller which translatesit into a percentage of air. If the percentage exceeds a predeterminedlevel, the user can be notified. Suitable bubble sensors can bephotosensitive or capacitive, and have a binary output (on and off),whereby the number of ons and offs are counted and converted to apercentage of air in a slug of fluid over time.

FIGS. 25A and 25B illustrate a valve design with no bubble traplocations. The fluid enters through the inlet of the valve and thenflows straight up along with all bubbles that also rise to the top. Theremainder of the flow path is a continuous diameter path with the sensorpocket detail all below the path so that no air can be trapped(conventional valves have features that create pockets where gas cannotescape). This design also eliminates three parts compared to theprevious embodiments, including a fluid diaphragm, a valve cap and abutton, to reduce assembly cost, part cost and complexity. Two criticalfluid seal locations alto are eliminated, including one of the diaphragmtongue and groove seals as well as the interference fit between twofluid diaphragms.

The valve functions by applying pneumatic pressure between the fluiddiaphragm 401 and the pneumatic diaphragm 402 to drive the valve openagainst a pre-loaded compression spring 800 biasing the valve closed.Because the pneumatic diaphragm 402 is larger than the fluid diaphragm401 and the two diaphragms are constrained to each other with screw 403and button 404, the pressure will create a greater load on the pneumaticdiaphragm 402 and force the valve open. Pressure is supplied throughbarb fitting 405 (FIG. 25B) and tubing (e.g., polyethylene) 406. Thepneumatic pressure cavity 410 is sealed with O-ring 407 and pneumaticdiaphragm tongue and groove as shown. A sensor 411 sealed with O-ring412 and secured with a sensor cap 413.

In another embodiment, to reduce 90° turns, the design can be modifiedas shown in FIG. 26, where the sensor cavity is moved to the side of thevalve. Offset flow paths eliminates turns, and eliminates un-sweptareas. The valve exhibits low hysteresis in view of the absence ofO-rings on the pneumatic side, and the design and sizing of thediaphragms with respect to each other. In view of the poppet design,excellent linearity is also achieved; the fluid flow rate issubstantially directly proportional to the pressure applied to the valvethroughout its working operation.

FIGS. 28A and 28B show another embodiment of the fluid control valvewhere an O-ring separates the fluid diaphragm from the pneumaticdiaphragm. This prevents excess loading on the two diaphragms that willcause a lower valve life expectancy. The flowpath of the fluid controlvalve is maintained with no high points for air to get trapped (exceptfor a minuscule amount that can collect where the sensor seals on theside of the fluid control valve body). The fluid control valve flowpathis designed with a single fluid diaphragm and no high points within thevalve (not including the pressure sensor sealing method) that are notdirectly in the fluid flow path where air could normally get trapped.Air trapped within the fluid control valve can be deleterious to the endof dispense once the fluid control valve closes and the air is able todecompress. The start of dispense can also be adversely affected by airtrapped in the fluid control valve. Air trapped in the fluid controlvalve may also contribute to additional air being dissolved into thefluid or micro-bubble formations that can cause defects on the wafer.

The valve functions by applying pneumatic pressure to the pneumaticcavity 410′ between pneumatic diaphragm 402′ and the pneumatic sealO-ring 415′ to drive the valve open against the pre-loaded compressionspring 800′ biasing the valve closed. The pressure applied to thesurface area of pneumatic diaphragm 402′ causes it to deflect forcingfluid diaphragm 401′ to also deflect and open as it is constrained topneumatic diaphragm 402′ with screw 403′ and button 404′. The pneumaticseal O-ring 415′ prevents pneumatic pressure from generating excess loadon the two diaphragms by not allowing any pneumatic pressure to reachthe fluid diaphragm. Pressure is applied through barb fitting 405′ andsuitable tubing, A sensor cavity 500 optionally may be located above thevalve seal. The design prevents air from becoming trapped in the fluidcavity, the inlet channel, the outlet channel, and the channel to thesensor cavity and the sensor cavity (if present). The fluid inletchannel is positioned tangent to the internal diameter of the valvefluid cavity 90′, as tangential flow prevents unswept areas. All highspots are within the fluid path, or are not higher than the fluid path.No sharp flow path corners are present. Fluid flow is gentle.

The various designs and flexibility thereof allow for modular assemblieswith numerous combinations of valves and sensors and provide for variousconfigurations, enabling the construction of valves, sensing devices,flow meters, flow controllers, pressure controllers and temperaturecontrollers. Thus, FIG. 20 shows a stacked flow controller and on/offvalve assembly including a first valve 300, a second valve 300′ andfirst and second sensors 310, 310′ in fluid communication with africtional flow element 15. FIG. 21 shows a stacked assembly of foursensing devices 310, 310′, 320 and 320′. FIG. 22 illustrates a flowcontroller and flow meter assembly.

FIGS. 24A, 24B illustrate a further embodiment of the molded valvedesign that is configured for a flow controller and has the ability tomate with an LHVD (low hold-up volume device) style filter devicethrough three ports located on the bottom of the device. Port 610 is avent from the filter, port 612 is an inlet to the filter, and port 614is an outlet from the filter.

In accordance with a further embodiment of the present invention, avalve assist function can be used. In conventional valves usingsolenoids, needle valves can be used to alter the change in pressureapplied to each valve, typically to dissipate that pressure slowly. Byreducing the rate of change applied to the suckback portion of the valveduring the stop portion of the sequence, the suckback valve assists thestop valve. In accordance with the present invention as shown in FIG.29, during the control valve (or stop valve) off time, the suckbackvalve pressure can be reduced as shown to assist the control valve. Oncethe control valve off time is terminated, a suckback delay is providedwhere the pressure to the suckback valve remains constant. After thispredetermined delay, the pressure applied to the suckback valve is againreduced until the suckback valve pressure reaches a predetermined level,returning the suckback valve to its normal or static position. Thissequence helps in keeping fluid drops from hanging off the nozzle. Inyet a further embodiment, the suckback assist action can be delayed tostart at a time following the control valve action, or can be shortenedso that the action of the suckback valve occurs at only the beginning ofthe stop action of the control valve. Although the foregoing recitespressure as the actuation method, it is within the scope of the presentinvention to use any valve actuation method, such as a motor.

EXAMPLE 1

The system was set up so that a known differential pressure and a fixeddispense time could be inputted to the controller, and a dispense couldbe subsequently triggered from a laptop computer. The resultant outputflow of deionized water was captured in a container and weighed using aprecision scale to determine its mass. Using the mass of each dispensecombined with the known density of the fluid material, the volume ofeach dispense was calculated. Combining the volume dispensed with theknown dispense time resulted in a flow rate determination. Fivedifferent viscosities were checked, ranging from about 0.92 to about 9.5centipoise. The results are shown graphically in FIG. 10.

EXAMPLE 2

Three different valves were tested for hysteresis, including twocommercially available valves, and the valve of the present inventionshown in FIGS. 8A-8D. The valve actuation pressure was varied up anddown and the pressure inside the test system was measured in steps upand down through the valve actuation pressure range and plotted asvoltage. More specifically, the test set-up was a closed system of thevalve and downstream pressure sensor, with the valve under constantpressure and the pressure sensor monitoring the change in pressuredownstream of the valve as the valve moved through its range of closedto full open and back again to closed.

The results are shown graphically in FIGS. 9A, 9B and 9C. In each graph,the curve farthest to the right represents the data for varying thepressure from low to high, and the curve to the left is the result ofvarying pressure from high to low. The difference between the curvesrepresents the amount of hysteresis. Thus, as the pressure is varied upand down in steps of actuation pressure, if there were no hysteresis,the two curves would exactly overlap. FIG. 9C shows that the valve ofthe present invention exhibits significantly less hysteresis than thecommercial valves.

EXAMPLE 3

This example illustrates the use of an embodiment of the presentinvention to measure and control liquid flow to enable the delivery ofdiscrete volumes of fluid for chemical mechanical planarizationsubstrate processing. More specifically, this example demonstrates howan embodiment of the present invention may be used to measure andcontrol liquid flow to enable the delivery of discrete volumes of apolishing fluid to a substrate.

Chemical mechanical polishing is useful in the manufacture of opticallenses. Chemical mechanical planarization is useful in the manufactureof semiconductor devices. Polishing fluids may be acidic or basic andmay contain abrasives such as silica or alumina. A fluid useful forpolishing silicon dioxide includes silica slurry in an aqueous potassiumhydroxide solution; a fluid useful for polishing copper metal includesan oxidizer such as hydrogen peroxide, an inhibitor such asbenzotriazole, and an aqueous solution of an organic acid such as aceticacid.

The inlet of the embodiment of the present invention is connected to apressurized or gravity feed vessel containing the polishing fluid. Theflow device outlet is connected to a nozzle on the polishing tool. Thepolishing tool has a substrate to be polished by a rotating pad or belt.The substrate is in contact with a polishing pad that removes materialfrom the substrate along with the chemical action of the polishingfluid. Polishing fluid is delivered to the substrate on the tool throughthe nozzle; flow of polishing fluid to the nozzle is controlled by theflow device and its electronics. The electronics of the flow device maybe connected to the tool's controller to enable the tool to control thetiming of the dispense of polishing fluid onto the substrate. The toolmay also contain a polishing endpoint detector that may also be used tocontrol the timing of the delivery of polishing fluid to the substrate.The signal processor in the electronics of the flow device eliminatesthe variability of polishing fluid volume and delivery rate due topressure variations in the pressurized vessel containing the polishingfluid. Compared to peristaltic pumps, delivery of polishing fluid occursat a constant rate. The result is controlled volume and delivery rate ofpolishing liquid to a substrate that minimizes chemical waste andresults in more uniform and repeatable polishing of the substrate.

EXAMPLE 4

This example illustrates the use of an embodiment of the presentinvention to measure and control liquid flow so that discrete volumes ofliquid precursors can be delivered to a vaporizer to form a gas. Morespecifically, this example demonstrates how an embodiment of the presentinvention may be used to measure and control the flow of liquidprecursors to a vaporizer.

Liquid precursors are chemicals that are heated in a vaporizer to form agas. The gas is then delivered to a heated substrate in a reactionchamber where it is further decomposed or reacts on the substrate. Thegas may be used to form a thin film of a metal, a semiconductor, or adielectric on the substrate (chemical vapor deposition or atomic layerchemical vapor deposition processes), it can be used to etch the surfaceof a substrate, or it can be used to dry the substrate. Liquidprecursors may be pure liquids such as water, 2-propanol, or tetraethylorthosilicate, TEOS. Liquid precursors may also contain solids such asstrontium dipivaloylmethane, Sr(DPM)₂, dissolved in a solvent such astetrahydrofuran. Some liquid precursors, such as copper (I)hexafluoropentanedionate vinyltrimethylsilane, (VTMS)Cu(hfac), arethermally sensitive and could be decomposed by thermal sensors used insome liquid flow meters. Liquid precursors are typically delivered tothe vaporizer at a rate of about 0.1 gram per minute to about 50 gramsper minute. Thin films are important in the coating of optical devicessuch as lenses and optical fibers. Thin films and thin film etching arealso important in the manufacture of flat panels, microprocessors, andmemory devices.

An embodiment of a flow device of the present invention is connected atits inlet to a pressurize source of liquid precursor. The outlet of theflow device is connected to a vaporizer. The valve for the flow devicecan be upstream or downstream of the vaporizer. The outlet of thevaporizer is connected to the tool's process chamber that contains thesubstrate to be treated by the vapor. For processes requiring multipleprecursors, multiple flow devices can be used. The electronics of theflow device may be connected to the tool's controller. This permits theprocess tool to remotely control the flow of liquid from the pressurizedsource through the flow meter and into the heated vaporizer. Examples ofvaporizers useful for chemical vapor deposition processes include heatedmetal frits, heated metal screens, heated valves, and heated tubing.

Pressure variations in the vessel containing the liquid precursor canresult in changes of liquid flow to the vaporizer. Thermal decompositionof a liquid precursor in a thermal flow element can result in inaccurateliquid flow to the vaporizer. Poor flow control to the vaporizer canresult in incomplete vaporization of the liquid due to vaporizersaturation. Incomplete vaporization will cause liquid droplets to enterthe process chamber and cause defects on the substrate. The result ofpracticing this invention embodiment is the elimination of thermal flowelement to control precursor flow and a repeatable and controlled flowof liquid to the vaporizer regardless of upstream pressure fluctuations.

EXAMPLE 5

This example illustrates the use of an embodiment of the presentinvention to measure and control liquid flow to enable the delivery offluid to a substrate for electroless plating. More specifically, thisexample demonstrates how an embodiment of the present invention can beused to measure and control liquid flow to enable the dispense of aseries of chemicals onto a substrate to form a metal film in platingprocesses. Such a process eliminates drag but bf chemicals common tobath plating processes.

Solutions of metals and metal alloys useful for plating include, but arenot limited to, silver, copper, platinum, palladium, gold and tin.Catalysts are often required to activate the substrates to the platingsolution. These catalysts include colloidal palladium, carbon, graphite,tin-palladium colloids, and conductive polymers such as polypyrrole. Theprecious metals in some of these catalysts and plating solutions areexpensive and waste during the plating process needs to be minimized tomake the plating process cost effective. The metals in some of thesesolutions are toxic and waste during the plating process needs to beminimized to reduce environmental discharge as well as waste processingand disposal costs.

For each chemical used in the plating process, an embodiment of thepresent invention is connected at its inlet to a pressurized, pump fed,or gravity fed source of the chemical. The outlet of the embodiment ofthe present invention is connected at its outlet to a nozzle fordelivering each chemical to the substrate. The temperatures of thesolutions may be decreased or increased prior to delivery to thesubstrate using a heat exchanger, chiller, or resistive heater element.Pot example, copper metal may be deposited onto a substrate by anelectroless process by contacting the substrate through a first flowdevice with an activator solution containing colloidal palladium,rinsing the substrate with water using a second flow device, contactingthe catalyzed substrate through a third flow device with a hydrochloricacid activating solution, contacting the substrate through a fourth flowdevice with a volume of copper solution containing a source of cupricion, a reducing agent like formaldehyde, a complexing agent like EDTA,and a base like potassium hydroxide. The substrate is washed with waterfrom the second flow device.

The electronics of the flow devices may be connected to the platingtool's controller to regulate the timing, duration, and order of liquidflow through each flow device. The result is rapid and precise deliveryof measured volumes of each chemical to the substrate for each step inthe process. Chemical waste and materials costs are minimized bydelivering only enough chemical to the substrate to ensure completereaction. Contamination of the substrate due to chemical drag out isreduced. The overall throughput of the process is increased because ofthe rapid action of the flow element and valve to reduce cycle time.

EXAMPLE 6

This example illustrates the use of an embodiment of the presentinvention, to measure and control liquid flow to enable delivery of afluid to a substrate to form a conformal coating. More specifically,this example demonstrates how an embodiment of the present invention canbe used to measure and control liquid flow to a substrate to enableprecise coating of the substrate with the liquid material.

Dielectric materials, photoresists, antireflective coatings, polyimides,adhesion promoters such as hexamethyldisilazane, ferroelectricmaterials, and sol-gels are commonly deposited as liquids or slurry ontoa substrate in a spin coating process. Such materials are delivered to astationary or slowly rotating substrate by a fixed or movable nozzle.After the material has been delivered to the substrate it is rotated athigh speeds ranging from about 100 to 5000 rpm to uniformly coat thesubstrate with a thin film of the liquid material. Many of thesematerials are costly and it is important to minimize their usage andwaste in the coating process. Repeatable coatings require thatconsistent volumes of material be delivered to the substrates.

The inlet of an embodiment of the flow device of the present inventionis connected to a pressurized or gravity fed vessel containing thecoating fluid. The flow device outlet is connected to a nozzle on thecoating tool. The coating tool has a substrate mounted to a rotatingchuck. The coating fluid is delivered to the substrate on the toolthrough the nozzle; flow of coating fluid to the nozzle is controlled bythe flow device and its valve. The electronics of the flow device may beconnected to the tool's controller to enable the tool to control thetiming and rate of coating fluid onto the substrate. By electroniccommunication with the flow device, the coating tool may vary the fluidflow rate onto the substrate as a function of nozzle position andsubstrate rotation rate in order to achieve a desired coating. Thesignal processor of the flow device eliminates the variability ofcoating fluid volume and delivery rate due to pressure variations in thevessel containing the coating fluid. The result is the delivery of acontrolled volume of coating fluid to the substrate. This resultminimizes chemical waste and results in more uniform and repeatablecoating of such substrates.

EXAMPLE 7

This example illustrates the use of an embodiment of the presentinvention to measure and control liquid flow to enable the delivery of afluid to a substrate for reaction with the substrate. More specifically,this example demonstrates how an embodiment of the present invention canbe used to measure and control the flow of a reactive liquid onto asubstrate. Examples of such reactive liquids include, but are notlimited to, positive or negative photoresist developers, photoresiststrippers, acids such as hydrofluoric acid, oxidants such as ozonateddeionized water, or etchants such as peroxyacetic acid.

The inlet of an embodiment of the flow device of the present inventionis connected to a pressurized or gravity fed vessel containing thereactive fluid. The flow device outlet is connected to a nozzle or aspray nozzle on the tool. The reactive fluid is delivered to thesubstrate on the tool through the nozzle; flow of reactive fluid to thenozzle on the tool is controlled by the flow device and its valve. Theelectronics of the flow device may be connected to the tool's controllerto enable the tool to control the timing and rate of reactive fluid flowonto the substrate. The electronics of the flow device may be connectedthrough the tool's controller to a reaction endpoint detector wherebythe flow rate of reactive fluid is reduced or stopped as the reactionendpoint is approached or is reached. An example of an etchant processis the removal of copper from the edges of plated wafers usingperoxyacetic acid. The result is the delivery of a controlled volume ofreactive fluid to the substrate and accurate control of the processendpoint using an embodiment of the present invention.

EXAMPLE 8

This example illustrates the use of an embodiment of the presentinvention in series with chemical sensors to measure and control liquidflow and composition. More specifically, this example demonstrates howan embodiment of the present invention can be combined with one or morechemical sensors to enable the control of fluid flow and fluidcomposition. Applications where such control is desirable include butare not limited to plating baths, RCA cleaning baths, ozonated waterbaths, and hydrofluoric acid baths. Other applications combining suchsensors with an embodiment of the present invention include maintainingthe purity of a chemical bath. For example, the build up of contaminantsin a recirculating bath, such as particles, organic materials, or metalions, may require that the bath be periodically bled of contaminatedfluid and replaced with an equivalent volume of uncontaminated fluid.Alternatively, the bath may be switched to a purifier or particle filterto remove the contaminants while maintaining a constant flow rate inorder to protect the current process and product until the contaminationcan be removed.

Ozone dissolved in deionized water is used for the removal of organicmaterials from the surfaces of various substrates. Fluctuations in ozonegenerator output gas concentration and water flow rate leads tovariations in dissolved ozone concentration. Such dissolved ozoneconcentration changes lead to variation in the time required to oxidizethe substrate surface with the ozonated water and causes inconsistentprocess results and cleaning times.

To maintain the concentration of dissolved ozone in an overflow cleaningbath an embodiment of the present invention is connected to a source ofdeionized water at its inlet and its outlet is connected to a gascontactor. A gas contactor is a mass transfer device capable ofdissolving gases into liquids. Examples of such devices and adescription of their operation are available from W. L. Gore, Elkton,Md., and Mykrolis Corporation, Bedford, Mass. Ozone gas from an ozonegenerator is delivered to the shell side of the gas contactor where itdissolves into the deionized water flowing through the tubes of the gascontactor. The concentration ozone dissolved in the water is measure bya dissolved ozone concentration monitor, available from IN USA, Needham,Mass., connected to the fluid outlet of the gas contactor. The outputsignal from the dissolved ozone concentration monitor is used as aninput signal into the electronics of the flow device of the presentinvention. The electronics of the present invention will vary the flowrate of water through the gas contactor, within preset limits, in orderto maintain the concentration of dissolved ozone within a predeterminedconcentration range. For example, if the concentration of ozone gasoutput from the ozone generator decreases, the flow of water through thegas contactor can be decreased by the flow device to maintain thedissolved ozone concentration.

Alternatively, the electronics of the flow device of the presentinvention can be used to vary the ozone generator gas flow rate, orpower level, by suitable means while maintaining a fixed water flow ratethrough the gas contactor regardless of water pressure upstream of theflow device. For example, if the concentration of dissolved ozoneexceeds a predetermined threshold while the flow of water is constant,the power to the generator can be decrease to reduce the concentrationof dissolved ozone back to its proper level.

The result is a controlled preparation and delivery of a chemicalmixture of constant composition to a substrate by the embodiment of theinvention.

EXAMPLE 9

This example illustrates the use of an embodiment of the presentinvention to measure and control liquid flow to enable the deliverycontrol low volumetric flows of an organic liquid.

A 40 inch length of PFA tubing having an inside diameter of 0.058 inchesand 14 twists was used as a pressure drop element. Temperature of theinlet fluid, 2-propanol, was about 23 degrees Celsius and was from asource vessel pressurized at about 20 pounds per square inch gauge.2-propanol flow rate as determined by the controller setpoint (SO) andvalve timing were controlled by an external computer. The mass of2-propanol delivered by an embodiment of the present invention wasmeasured on an Ohaus Analytical Plus Balance and the mass recorded as afunction of time on a second computer using the balance's RS232 port. Aplot of 2-propanol mass versus time is shown in FIG. 11. Also shown inFIG. 11 are the best fit lines for each of the dispense segments; theslope in the best fit line for each segment is the 2-propanol flow ratein grams per second. The results show a flow system capable ofdelivering a liquid at flow rates ranging from 0.0083 grams per second(0.16 grams per minute) to about 0.49 grams per second (9.6 grams perminute). Such a flow system is capable of controlling liquid at flowrates suitable for chemical vapor deposition processes.

1. A proportional fluid control valve, comprising a fluid inlet, a firstannular cavity in fluid communication with said fluid inlet, an annularfluid passageway in fluid communication with said first annular cavity,a second annular cavity in fluid communication with said annularpassageway, and a fluid outlet in fluid communication with said secondannular cavity.
 2. The proportional fluid control valve of claim 1,further comprising a pneumatic cavity in fluid communication with apneumatic inlet, and at least one diaphragm in said first annularcavity, whereby pneumatic pressure applied to said pneumatic cavitydeflects said diaphragm and opens said valve.
 3. The proportional fluidcontrol valve of claim 2, further comprising a spring that biasesagainst said diaphragm and maintains said valve in a normally closedposition until said bias is overcome by said pneumatic pressure.
 4. Theproportional fluid control valve of claim 1, further comprising a firstsensor housing in fluid communication with said fluid outlet, said firstsensor housing having a sensor housing fluid outlet; and a second sensorhousing in fluid communication with said sensor housing fluid outlet. 5.The proportional fluid control valve of claim 4, wherein said firstannular cavity, said second annular cavity, said first sensor housingand said second sensor housing are an integral molded component.
 6. Theproportional fluid control valve of claim 4, further comprising africtional flow element between said sensor housing fluid outlet andsaid second sensor housing.
 7. The proportional fluid control valve ofclaim 1, wherein said fluid inlet defines a first horizontal plane, saidfluid outlet defines a second horizontal plane, and wherein said firstand second horizontal planes do not intersect.
 8. A valve, comprising avalve housing having a pneumatic cavity, a pneumatic diaphragm in saidpneumatic cavity adapted to deflect upon the application of pressure tosaid pneumatic cavity, a first valve cavity, a first diaphragm in saidfirst valve cavity, a second valve cavity, a second diaphragm in saidsecond valve cavity, and a spring biasing said second diaphragm toprevent fluid communication between said first and second valve cavitiesuntil said bias is overcome by said application of pressure.
 9. Thevalve of claim 8, wherein said first and second valve cavities areannular, and wherein said first cavity is in fluid communication with alinear fluid inlet path, and said second annular cavity is in fluidcommunication with a linear fluid outlet path.
 10. The valve of claim 9,further comprising a pressure sensor in said linear fluid outlet path.11. The valve of claim 9, wherein fluid enters said first annular cavityfrom said fluid inlet path and remains therein until the pneumaticpressure applied to said pneumatic diaphragm overcomes the bias of saidspring.
 12. The valve of claim 9, wherein said fluid inlet path definesa first horizontal plane, said fluid outlet path defines a secondhorizontal plane, and wherein said first and second planes do notintersect.
 13. A stacked valve assembly, comprising a first proportionalfluid control valve comprising a first fluid inlet, a first annularcavity in fluid communication with said first fluid inlet, a firstannular fluid passageway in fluid communication with said first annularcavity, a second annular cavity in fluid communication with said firstannular passageway, a first fluid outlet in fluid communication withsaid second annular cavity, a first sensor housing in fluidcommunication with said first fluid outlet, said first sensor housinghaving a first sensor housing fluid outlet; and a second sensor housingin fluid communication with said first sensor housing fluid outlet; anda second proportional fluid control valve in vertical alignment withsaid first proportional fluid control valve, and second proportionalfluid control valve comprising a second fluid inlet, a second annularcavity in fluid communication with said second fluid inlet, a thirdannular fluid passageway in fluid communication with said second annularcavity, a fourth annular cavity in fluid communication with said secondannular passageway, a second fluid outlet in fluid communication withsaid fourth annular cavity, a third sensor housing in fluidcommunication with said second fluid outlet, said third sensor housinghaving a third sensor housing fluid outlet; and a fourth sensor housingin fluid communication with said third sensor housing fluid outlet,wherein said, first and second sensor housings are in vertical alignmentwith said third and fourth sensor housings, respectively.
 14. Thestacked valve assembly of claim 13, further comprising a firstrestrictive flow element between said first and second sensor housingsand a second restrictive flow element between said third and fourthsensor housing.
 15. A valve, comprising a valve housing having apneumatic cavity, a pneumatic diaphragm in said pneumatic cavity adaptedto deflect upon the application of pressure to said pneumatic cavity, avalve cavity, a valve diaphragm in said valve cavity, said valvediaphragm being secured to said pneumatic diaphragm, and a springbiasing said pneumatic diaphragm and said valve diaphragm to preventfluid flow out of said valve cavity until said bias is overcome by saidapplication of pressure.
 16. The valve of claim 15, further comprising asensor cavity.
 17. The valve of claim 16, and wherein said sensor cavityis positioned above where said valve diaphragm seals.
 18. The valve ofclaim 15, further comprising a fluid inlet tangential to said valvecavity.
 19. The valve of claim 15, wherein said valve cavity is in fluidcommunication with a fluid inlet and a fluid outlet, and wherein saidfluid inlet defines a first horizontal plane, said fluid outlet definesa second horizontal plane, and wherein said first and second planes donot intersect.